The present invention relates to an improvement of a seal structure, particularly a seal structure to be used with a hydraulic cylinder or the like.
Heretofore, there have been seal structures of a bearing section of a hydraulic cylinder or the like which has been disclosed in Japanese Utility Model Laid-Open Publication No. Hei 4-138160 and in which a backup ring is installed so as to prevent a heel section of a seal ring from projecting, and which has been disclosed in Japanese Patent Publication No. Hei 6-100202 and in which an unloading pressure control valve (buffer ring) is provided so as to reduce a pressure which acts on a seal ring.
However, in such conventional seal structures, for example, in the one which is disclosed in Japanese Utility Model Laid-Open Publication No. Hei 4-138160, the inner diameter and the outer diameter of an insertion groove of the seal ring are parallel to each other. A pressure receiving area of the seal ring in an axial direction extends over an entire surface of the inner diameter and outer diameter of a lip, whereby a supporting area of the heel section is almost the same as the pressure receiving area.
Thus, there have been problems such that a pressure of the heel section becomes high when a pressure is high and a deformation projecting into a sliding surface and a pressure grade to the sliding surface are great. Thus, a capacity of scraping of a hydraulic operating fluid film is great and oil leakage arises resulting from the scraping.
Further, the constitution is such that the higher a pressure becomes, the greater the capacity of scraping of a hydraulic operating fluid film becomes. Therefore, there will be problems such that a sliding section enters a non-lubricating state, friction increases, further frictional heat arises, thermal decomposition of the sliding section arises, and abnormal abrasion arises.
Further, in the constitution which is disclosed in Japanese Patent Publication No. Hei 6-100202 and in which the buffer ring and the seal ring are combined, the buffer ring is not constituted such that the buffer ring is completely airtight so as to secure a hydraulic operating fluid film. Therefore, there will be problems such that for example, in a flow regenerative circuit in which the pressure of an oil room on the side of a rod becomes high in either case of the expansion and shrinkage of a hydraulic cylinder, a pressure between the seal ring and the buffer ring is accumulated and it is impossible to prevent a high pressure from acting on the seal ring when a load pressure operates for a long period of time.
An object of the present invention is to provide a seal structure which solves these problems.
In order to solve the problems mentioned above, the present invention is made and characterized in that in seal structure which is composed of a sliding member, a supporting member for supporting the sliding member slidably, and a seal ring provided between the sliding member and the supporting member, the seal ring is stored in a storage concavity section and has a lip section on which a pressure of a hydraulic operating fluid acts and a heel section for supporting on a side wall surface of the storage concavity section a pressure which acts on the seal ring, and an annular pressure receiving area between an inner circumference and an outer circumference of the lip section is rendered to be smaller than an annular supporting area between an inner circumference and an outer circumference of the heel section.
The constitution is such that the seal ring is provided either at the supporting member or the sliding member.
Thus, since the pressure receiving area of the lip section is smaller than the supporting area of the heel section, when a pressure of the hydraulic operating fluid acts on the lip section, thrust to deform the seal ring becomes small. Moreover, since the supporting area of the heel section is larger than the pressure receiving area of the lip section, a pressure which arises at the heel section is reduced. Thus, it is possible to prevent the heel section from projecting into a sliding surface, whereby reliability on resistance to oil leakage can be enhanced. Further, since a pressure of the heel section can be reduced in a constant ratio, it is possible to prevent the heel section from coming into contact with the sliding surface when a high pressure acts and the friction can be reduced. Also, since a pressure of the heel section is rendered to be small, it is possible to make a critical working pressure of the seal ring higher and to eliminate a pressure reducing mechanism, such as a buffer ring. Therefore, a size of the seal in a sliding direction can be reduced and entire seal structure can be miniaturized. Since a shape of the seal is not symmetrical, it is possible to expect such effects that an error in assembling the seal ring can be prevented and sealing performance can certainly be secured.
Since the heel section of the seal ring is composed of a tapered surface which is away from the lip section in an opposite direction toward the sliding surface of the seal ring, deformation force of the seal is released in a direction of a bottom of a groove when a high pressure acts on the seal, the pressure is more uniformly distributed over the supporting surface, and it is possible to prevent the heel section from projecting into or sticking to the sliding surface.
It is constituted such that the heel section of the seal ring and a retaining member to retain the heel section are provided at the storage concavity section, and a space which becomes larger in an opposite direction toward the sliding surface of the heel section is provided when a pressure of a hydraulic operating fluid is not acting on a contact surface of the heel section and the retaining member. Therefore, the seal is certainly deformed in an opposite direction toward the sliding surface and a deformation of the seal on the sliding member side is suppressed, whereby a pressure and a pressure grade to the sliding member is hardly affected by a working pressure and a very stable sealing function can be realized.
It is constituted such that a tapered surface is formed at an outer circumference of a middle section which connects the lip section and the heel section of the seal ring. Therefore, a pressure of the lip section does not directly act on the supporting surface of the heel section, the distribution of a pressure is dispersed along the tapered surface, and it is possible for the heel section to have a uniform distribution of the pressure extending over an entire supporting surface of the heel section.
There is provided a hydraulic operating fluid draining groove for leading to the heel section a hydraulic operating fluid which exists between the tapered surface of the middle section and an inner circumferential section of the storage concavity to store the seal ring. Therefore, even though a high pressure which acts on the lip section leaks out to the tapered surface, it is possible to discharge the pressure to the side of the heel section under an atmospheric pressure using the hydraulic operating fluid draining groove. Thus, it is possible to prevent the tapered surface from being added to a pressure receiving area of the lip section on which a high pressure acts.
A space is provided between an inner circumference on the heel section side and a piston rod, and also a predetermined space for absorbing a deformation of the seal ring is formed between an outer circumference of the heel section and an inner circumference of the storage concavity section.
A space is provided between an inner circumference on the heel section side and the piston rod, a pressure receiving area of the lip section and a supporting area of the heel section are almost identically formed, and a predetermined space for absorbing a deformation of the seal ring is formed between an outer circumference of the heel section and an inner circumference of the storage concavity section.
It is constituted such that a total capacity of the aforementioned spaces provided between the inner circumference on the heel section side and the piston rod and between the outer circumference of the heel section and the inner circumference of the storage concavity section is 10 to 35 percent of a volume of an annular cylindrical body which is under projection of the pressure receiving area of the lip section, and a capacity of the space provided between the outer circumference of the heel section and the inner circumference of the storage concavity section is 0.6 times more than that of the space provided between the inner circumference of the heel section and the piston rod.
It is constituted such that the total capacity of the spaces provided between the inner circumference on the heel section side and the piston rod and between the outer circumference of the heel section and the inner circumference of the storage concavity section is 20 to 45 percent of a volume of the seal ring, and a capacity of the space provided between the outer circumference of the heel section and the inner circumference of the storage concavity section is 1.0 time more than that of the space provided between the inner circumference of the heel section and the piston rod.
The space between an outer circumference of the heel section and an inner circumference of the storage concavity section is provided in a shape of concavity at the storage concavity section of a cylinder head.
The space between the outer circumference of the heel section and the inner circumference of the storage concavity section is provided in a shape of concavity at the seal ring.
An outer circumference of the heel section of the seal ring has a shape of taper.
There is provided an annular groove which forms a plurality of spaces between the outer circumference of the heel section of the seal ring and the storage concavity section.
A middle section in a shape of taper is formed between the lip section and the heel section of the seal ring, and a space is provided between the middle section of the seal ring and an inner circumference of the storage concavity section which faces the middle section.
The middle section of the seal ring and an inner circumference of the storage concavity section which is in contact with the middle section are formed in a shape of arc.
An outer circumference of the heel section of the seal ring is formed by a plurality of step sections which have different diameters.
Due to the constitution described above, a space having a capacity corresponding to a volume of the deformation of the seal ring resulting from a pressure which acts on the lip section is provided on the outer circumference side of the heel section, a deformation of the seal ring resulting from the working pressure is led to the space, and a deformation to the inner circumference side of the seal ring can be made small to such an extent that can almost be ignored. Therefore, interference of the heel section and the piston rod can be prevented and it is possible to eliminate nonconformity, such as abnormal abrasion or deterioration of durability of the seal ring resulting from frictional heat or an increase in friction.
Further, it is possible to deter a deformation of the heel section to the piston rod side. Therefore, pressure resistance can be improved, and also sealing performance and durability can be secured even under the condition of a high pressure which is higher than usual.
There is provided a pressure draining hole to discharge a pressure which exists between an outer circumference of the seal ring and an inner circumference of the storage concavity section to store the seal ring in such a manner that the pressure draining hole penetrates the cylinder head.
There is provided a pressure draining groove to lead to the heel section side a pressure which exists between an outer circumference of the seal ring and an inner circumference of the storage concavity section to store the seal ring.
Since the pressure draining hole is provided at a supporting member or the pressure draining groove is provided at the seal ring, a pressure in the space can be discharged to the side of an atmospheric pressure utilizing the pressure draining hole or the pressure draining groove and it is possible to prevent a fluid remaining in the space from hindering a deformation of the seal ring.
An elastic member which allows and absorbs a deformation of the seal ring to the outer circumference side is arranged in the space for absorbing a deformation of the seal ring.
A void is provided at least either between the elastic member and the seal ring or between the elastic member and the supporting member.
The elastic member is closely stored in a space section.
Due to the constitution described above, the seal ring is composed of its body and an elastic member which is provided at an outer circumference of the body, and by taking a shape of the elastic member, characteristic of the material, a capacity of the space section, or the like into consideration, a deformation to the outer circumference side is allowed in proportion to a pressure which acts on the lip side and also the deformation can be absorbed, whereby it is possible to make the change of a size of the inside diameter almost zero. Thus, contact or engagement with the piston rod can be prevented and the problems, such as an increase in friction or oil leakage can be solved.
Further, the elastic member and the seal ring are different parts, and therefore it is possible to freely control a deformation of the seal ring by freely changing the shape or material of the elastic member.
Further, since the seal ring and the elastic material are divided, shapes of the respective parts can be simplified, whereby expenses for dies will be reduced and work efficiency will be improved.
By holding down a variation in size of the inside diameter of the seal ring, a stress which arises at an inside diameter section can be decreased, fatigue strength of the seal improves, and durability improves.
Further, by providing predetermined spaces on the inner circumference side and the outer circumference side of the elastic member and in combination with the elastic characteristic of the elastic member, it is also possible to control a deformation of the seal ring.
There is provided a communicating hole for connecting a oil room and the storage concavity section to which an outer circumference of the lip section of the seal ring adheres closely. The communicating hole has a diameter almost same as that of the storage concavity section.
A constricted part is provided at an outer circumferential section which exists between the lip section and the heel section of the seal ring, and an annular pressure receiving area between an inner circumference and an outer circumference of the constricted part is formed to be smaller than an annular supporting area between an inner circumference and an outer circumference of the heel section. Further, there is provided a communicating hole for connecting a oil room and the storage concavity section which adheres closely to an outer circumference of the lip section of the seal ring. The communicating hole has a size larger than an outside diameter of the constricted part.
In a seal ring, a pressure receiving area of a lip section or a constricted part on which a pressure of a lubricating material acts is smaller than a supporting area of a heel section. A storage concavity of a supporting member in which the seal ring is stored is formed so that an oil room and the storage concavity section which adheres closely to an outer circumference of the lip section are connected via a communicating hole having a diameter almost same as an inside diameter of the storage concavity section or larger than an outside diameter of the constricted part.
In order to assemble the seal ring, it will be sufficient if the seal ring passes through the communicating hole and the storage concavity section of a supporting member which is in contact with an outer circumference of the lip section of the seal ring. Thus, it is possible to hold down the quantity of deformation of each part, whereby damage of parts will be prevented, precision in assembling parts will be increased, and work efficiency will be improved. Further, a cutting amount in boring can be reduced and it is possible to increase processing precision or reduce expenses for processing.
Cutting work of the storage concavity section adherent closely to the outer circumference of the lip section which will be a great contribution to the sealing performance can be changed from boring to ordinary inside diameter processing. This produces such effects that roughness of a surface to be processed and dimensional accuracy can be increased and the management can be facilitated.
Since the pressure receiving area of the lip section is smaller than the supporting area of the heel section, even though a high pressure of a hydraulic operating fluid directly acts on the lip section without buffer ring, thrust to deform the seal ring becomes small. Moreover, since the supporting area of the heel section is larger than the pressure receiving area of the lip section, a pressure which arises at the heel section is reduced. Therefore, it is possible to prevent the heel section from projecting into the sliding surface and improve reliability on resistance to oil leakage can be enhanced. Further, since a pressure of the heel section can be reduced in a constant ratio, it is possible to restrain the heel section from coming into contact with the sliding surface when a high pressure acts, and friction can be reduced.
Further, a shape of the seal ring is not symmetrical with respect to a direction perpendicular to a central axis of the sliding member, and therefore there is expectation of such an effect that an error in assembling the seal ring is prevented.
In addition, a pressure which acts on the lip section is also reduced because the pressure receiving area becomes small, and a level of pressure resistance of the supporting member can be reduced. As a result, it is possible to make an outside diameter of the supporting member small, thereby being effective in reducing the weight of the supporting member and lowering costs.
In addition to the effects described above, since a dimensional regulation of the lip section is released, an effect of enhancing a degree of freedom of shape is produced.
There is provided a hydraulic operating fluid draining hole, which penetrates the supporting member and fronts on the outer circumferential section of the seal ring, for discharging a hydraulic operating fluid which exists between the outer circumferential section of the seal ring and the inner circumferential section of the storage concavity section to store the seal ring.
Further, there is provided a hydraulic operating fluid draining groove for leading to the heel side a hydraulic operating fluid which exists between the outer circumferential section of the seal ring and the inner circumferential section of the storage concavity section to store the seal ring.
Since the hydraulic operating fluid draining hole is provided at the supporting member or the hydraulic operating fluid draining groove is provided at the seal ring, even though a high pressure which acts on the lip section leaks out to a tapered surface, the pressure can be discharged to the atmospheric pressure side using the hydraulic operating fluid draining hole or the hydraulic operating fluid draining groove. Thus, it is possible to prevent the tapered surface from being added to the pressure receiving area of the lip section on which the high pressure acts.